The objective of this research is to evaluate the fungus Lagenidium giganteum, a pathogen of mosquito larvae, and develop practical methods for its use in the control of mosquitoes which are important vectors of human and livestock diseases. Included are studies on persistence and overwintering in standing water, survival through drying cycles in temporary water and comparisons of methods of introduction (single versus multiple). Experiments will be conducted in natural mosquito breeding sites and in experimental ponds. Field experiments will involve several species of Culex, Aedes and Anopheles mosquitoes in differing types of habitats. Evaluations of the tolerances of different isolates to environmental extremes (temperature, salinity, organic pollution) will be included.